Large scale heat exchangers incorporating discrete, individually replaceable tube assemblies having a tube to convey a first fluid, and secondary heat transfer surface area for a second fluid transferring heat to or from the first fluid, are well known. As an example, heat exchangers of this type functioning as heavy duty equipment radiators to transfer waste heat from engine coolant to air have been described in U.S. Pat. No. 3,391,732 to Murray, and U.S. Pat. No. 4,236,577 to Neudeck. The tube assemblies used in these heat exchangers have a central finned section for heat exchange, and un-finned cylindrical end sections for insertion into sealing grommets.
Heat exchanger tube assemblies of the kind described above are typically constructed of copper, with the extended air-side surfaces in the finned region being soldered to the tube. Copper provides the advantages of high thermal conductivity, easy manufacturability, and good strength and durability. However, the steadily increasing price of copper has led to a demand for alternate, lower cost materials.
Aluminum has replaced copper as the preferred material of construction in other heat exchangers (automobile and commercial radiators, for example), but has not successfully replaced copper in heavy duty heat exchangers of this kind Aluminum has substantially lower strength than copper, leading to durability concerns. This is especially problematic in applications where individual tube assemblies need to be removed and inserted in the field, as damage is likely to occur during such handling. Furthermore, the bonding of aluminum components requires substantially higher temperatures than the soldering of copper, leading to manufacturing difficulties. Thus, there is still room for improvement